1. Field of Invention
The present invention relates generally to the field of fluid sample handling and/or interfacial rheology measurement at temperature and pressure conditions existing at the source of the sample, or at least temperatures different than ambient, including, but not limited to, reservoir hydrocarbon and aqueous based fluids, drilling muds, frac fluids, and the like having multiple phases (solids and liquid).
2. Related Art
The desirability of taking downhole formation fluid samples for chemical and physical analysis has long been recognized by oil companies, and such sampling has been performed by the assignee of the present invention, Schlumberger, for many years. Samples of formation fluid, also known as reservoir fluid, are typically collected as early as possible in the life of a reservoir for analysis at the surface and, more particularly, in specialized laboratories. The information that such analysis provides is vital in the planning and development of hydrocarbon reservoirs, as well as in the assessment of a reservoir's capacity and performance.
The process of wellbore sampling involves the lowering of a sampling tool into the wellbore to collect a sample or multiple samples of formation fluid by engagement between a probe member of the sampling tool and the wall of the wellbore. Many known sampling tools create a pressure differential across such engagement to induce formation fluid flow into one or more sample chambers within the sampling tool. This and similar processes are described in U.S. Pat. Nos. 4,860,581; 4,936,139 (both assigned to Schlumberger); U.S. Pat. Nos. 5,303,775; 5,377,755 (both assigned to Western Atlas); and U.S. Pat. No. 5,934,374 (assigned to Halliburton). Other examples of downhole sampling tools are disclosed in U.S. Pat. Nos. 6,223,822; 6,457,544; 6,668,924, and published U.S. patent applications 20050082059; 20050279499; and 20060175053, all assigned to the assignee of the present invention. These references are incorporated herein by reference for their disclosure of downhole sampling tools. The desirability of housing at least one, and often a plurality, of such sample chambers, with associated valving and flow line connections, within “sample modules” is also known. Each type of sampling tool provides certain advantages for certain conditions. The tools described in the art are typically probe sampling tools for new wells that have just been drilled, are full of over balanced mud and have a sealing mudcake between the higher pressured wellbore and the lower pressured reservoir. This invention is for a producing well with mud removed, no mudcake, and the pressure in the wellbore less than the reservoir pressure. It is annular fluid sampling that is augmented by the heat delivered with the insulated coil, not probe sampling. however, for oils having viscosity above 1000 cp, the existing sampling methods and tools may not be adequate.
As sources of light hydrocarbon oil are depleted with time, heavy oil has for several years now been gaining the attention of oil companies. Heavy oil reservoirs need thermal stimulation to reduce viscosity of the heavy oil so the oil may flow. The viability of developing a new heavy oil reservoir depends on the oil's viscosity change with temperature. This fluid property is different for different heavy crude oils, and is typically measured in a laboratory on a fluid sample. This measurement is necessary to make a financial model of the heavy oil development, as generating the amount of heat required for flow is the major portion of the cost of production. This in turn has generated a need in the art for obtaining heavy oil samples from the reservoir. Obtaining this sample itself requires heat, as without it the oil will not flow, and this means that heavy oil sampling requires in situ heating.
Although it is possible to heat a portion of a reservoir, using for example electric coils, and then take a sample from that region using a sampling device, it is not an easy proposition, since it is not possible to supply enough power with cables. More power, in the form of heat/hour, can be delivered by pumping a very hot fluid. Pumping heated oil from the surface down conventional tubing to supply heat is not a viable option, however, since fluids heated at the surface lose most of their heat due to heat transfer by the time they reach the sampling region, which may be thousands of meters into a wellbore. Therefore, a long but as yet unmet need exists in the art for a method of applying heat to a portion of a heavy oil reservoir in the region of the reservoir where it is desired to take a sample concurrent with the deployment of a sampling tool in that same region, and actually sampling the reservoir with a device or portion thereof that is used to supply heat to the region of the reservoir of interest. It would further be advantageous if this could be accomplished while reservoir fluids are being pumped to surface.